The present invention relates to a balancer integrated with a crankcase of an internal combustion engine which is capable of reducing second order vibration that is caused in the internal combustion engine.
Japanese Patent Application Unexamined Publication No. 2009-68364 discloses a balancer integrally coupled to a crankcase that is mounted to a lower portion of a cylinder block of an internal combustion engine. The balancer is constructed such that a rotational force is transmitted from the crankshaft to a drive balance shaft and a driven shaft through a timing chain. The balance shafts have balance weights, respectively, which make a unitary rotation with the balance shafts and serve to effectively reduce second order vibration of the engine. Further, the timing chain always undergoes a constant tension produced by a tensioner that is disposed on the crankcase to thereby enhance transmission ability of transmitting the rotational force from the crankshaft.